Method and device for accurately controlling reduction valence state of high-purity vanadium pentoxide

ABSTRACT

The present application relates to the technical field of non-ferrous metal reduction, and specifically to a method and device for accurately controlling a reduction valence state of high-purity vanadium pentoxide. An example method includes: introducing a reducing gas into the vanadium pentoxide to carry out a reduction reaction under a heating condition to obtain a mixture; weighing the mixture during the reduction reaction, and stopping the reaction when the weight of the mixture reaches a specified value; and introducing a cooling gas into the mixture for cooling to obtain calcine. An example device includes: a conveying member; a casing arranged on the conveying member; a partition member on the casing and dividing the inside of the casing into a reduction zone and a protection cooling zone; a material storage member on the conveying member for placing materials; and a weighing member on the conveying member.

RELATED APPLICATIONS

This application claims priority to and the benefit of Chinese Patent Application No. 202210068678.8, filed on Jan. 20, 2022, the disclosure of which is expressly incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present application relates to the technical field of non-ferrous metal reduction, and in particular to a method and device for accurately controlling a reduction valence state of high-purity vanadium pentoxide.

BACKGROUND

Flow batteries are a kind of large-scale energy storage devices, which contain active substances, and can store energy and discharge energy in a flowing state. In recent years, with the development of renewable energy such as wind energy and solar energy, the large-scale energy storage performance of flow batteries makes them have good development prospects. So far, a variety of battery systems have been made using flow batteries, among which an all-vanadium redox flow battery system is the most mature system.

Commonly used all-vanadium redox flow batteries generally adopt a tetravalent vanadium electrolyte as a raw material. However, the tetravalent vanadium electrolyte needs to be activated when it is used, while the electrolyte of 3.5-valence vanadium does not need to be activated. The positive and negative valence state can be matched with the material when it is charged for the first time, and it can be used directly. Therefore, the preparation of 3.5-valence vanadium is the key to the preparation of all-vanadium redox flow batteries.

The preparation method of 3.5-valence vanadium commonly used is as follows: using a vanadium-containing leaching solution as a raw material, a 3.5-valence vanadium solution is obtained through reduction, concentration and purification; and under a high vacuum condition, the solution is put in liquid nitrogen, so that the water in the frozen body is sublimated to make the solution dry into a powdery material. This method has a complicated process flow, and it is difficult to remove impurities, resulting in a relatively low purity of 3.5-valence vanadium.

SUMMARY

In order to improve the purity of target valence state vanadium, the present application provides a method and device for accurately controlling a reduction valence state of high-purity vanadium pentoxide.

In a first aspect, the present application provides a method for accurately controlling a reduction valence state of high-purity vanadium pentoxide, and adopts the following technical solution:

A method for accurately controlling a reduction valence state of high-purity vanadium pentoxide, comprising the following steps:

-   reduction: introducing a reducing gas into the vanadium pentoxide to     carry out a reduction reaction under a heating condition to obtain a     mixture; -   weighing: weighing the mixture during the reduction reaction, and     stopping the reaction when the weight of the mixture reaches a     specified value; and -   cooling: introducing a cooling gas into the mixture for cooling the     mixture to obtain calcine.

By adopting the above-mentioned technical solution, the reducing gas is introduced into vanadium pentoxide; the mass of target valence state vanadium completely generated, which is a specified value, is calculated according to the added reducing gas; and during the reduction reaction, the mixture is weighed, and when the weight of the mixture reaches the specified value, the reduction reaction is stopped, and the cooling gas is introduced to cool and protect the mixture, so as to avoid oxidation of the mixture and obtain the calcine. In the method of the present application, the progress of the reaction is judged according to the change of the weight of the reduction reaction product, which reduces the generation of non-target valence state vanadium, and thus improves the purity of the target valence state vanadium in the calcine.

In a specific embodiment, the reducing gas is one of hydrogen, carbon monoxide and sulfur dioxide.

By adopting the above-mentioned technical solution, hydrogen, carbon monoxide and sulfur dioxide all can reduce vanadium pentoxide. In the present application, hydrogen is preferable, the reducing effect of hydrogen is better, and compared with carbon monoxide and sulfur dioxide, hydrogen has no toxicity, which improves the safety of production.

In a specific embodiment, a rate at which the reducing gas is introduced is 1 to 500 ml/min.

By adopting the above-mentioned technical solution, when the rate at which the reducing gas is introduced is less than 1 ml/min or greater than 500 ml/min, more by-products may be generated, which thus affects the purity of target valence state vanadium in the calcine. In the present application, the rate at which the reducing gas is introduced is 1 to 500 ml/min, which improves the purity of target valence state vanadium in the calcine.

In a specific embodiment, a heating method in the reduction step is to carry out heating by means of a silicon carbon rod, and the heating temperature is 300 to 1200° C.

By adopting the above-mentioned technical solution, when the heating temperature is less than 300° C., the rate of reduction reaction is slower, when the reaction temperature is higher than 1200° C., more by-products may be generated, which affects the purity of target valence state vanadium in the calcine. In the present application, the heating temperature is 300 to 1200° C., which not only increases the reaction rate, but also improves the purity of target valence state vanadium in the calcine.

In a specific embodiment, the cooling gas is nitrogen or an inert gas.

By adopting the above-mentioned technical solution, both nitrogen and inert gas can be used for cooling and protection of the product. In the present application, nitrogen is preferred, and nitrogen is safer, which improves the safety of production.

In a second aspect, the present application provides a device for accurately controlling a reduction valence state of high-purity vanadium pentoxide, and adopts the following technical solution:

A device for accurately controlling a reduction valence state of high-purity vanadium pentoxide, comprising a conveying member and a casing arranged on the conveying member, wherein a partition member is provided on the casing; the partition member divides the inside of the casing into a reduction zone and a protection cooling zone; a material storage member for placing materials is provided on the conveying member; and a weighing member is provided on the conveying member.

By adopting the above-mentioned technical solution, vanadium pentoxide is placed on the material storage member, the conveying member conveys vanadium pentoxide to the reduction zone, the reducing gas is introduced into the reduction zone, and the weighing member is used to weigh the mixture on the material storage member. When the weight of the mixture on the material storage member reaches a specified value, the conveying member is used to convey the mixture to the protection cooling zone, and the cooling gas cools and protects the product to obtain the target valence state vanadium.

In a specific embodiment, the conveying member comprises a chain conveyor, and the casing is arranged on a frame of the chain conveyor; the partition member comprises a partition plate arranged on an inner top wall of the casing, and the partition plate divides the inside of the casing into the reduction zone and the protection cooling zone; and the material storage member comprises a material tray placed on the chain conveyor, the material tray is located between two adjacent power rollers on the chain conveyor, and both ends of the material tray extend out along a width direction of the chain conveyor.

By adopting the technical solution, the material tray is placed between two adjacent power rollers on the chain conveyor, which facilitates both the conveyance of the material tray by the chain conveyor and the removal of the material tray from the chain conveyor.

In a specific embodiment, the weighing member comprises a load cell arranged on the frame of the chain conveyor; a weighing end of the load cell is connected with a connecting plate; the connecting plate is connected with two electric cylinders; telescopic rods of the two electric cylinders are each connected with a vertical plate; and the two vertical plates are used to lift the material tray.

By adopting the above-mentioned technical solution, when the material tray is positioned above the vertical plates, the chain conveyor stops conveying, and the telescopic rods of the two electric cylinders simultaneously drive the vertical plates to rise. The vertical plates lift the material tray, and the load cell carries out weighing to complete the weighing of the mixture.

In a specific embodiment, the material tray is made of zirconia or alumina.

By adopting the technical solution, the melting point of zirconia and alumina is relatively high, so that vanadium pentoxide on the material tray can react at high temperature.

In a specific embodiment, a gas pressure in the protection cooling zone is greater than a gas pressure in the reduction zone.

By adopting the above-mentioned technical solution, when the reducing gas and the cooling gas are introduced, it is ensured that the pressure of cooling gas is greater than the pressure of reducing gas to prevent the reducing gas from entering in protection cooling zone, so that the mixture in the protection cooling zone will not undergo a reduction reaction again, which improves the purity of target valence state vanadium in the calcine.

In summary, the present application includes at least one of the following beneficial technical effects:

-   1. In the method of the present application, the progress of the     reaction is judged according to the change of the weight of the     reduction reaction product, which reduces the generation of     non-target valence state vanadium, and thus improves the purity of     the target valence state vanadium in the calcine. -   2. In the present application, the reducing gas is preferably     hydrogen, the reducing effect of hydrogen is better, and compared     with carbon monoxide and sulfur dioxide, hydrogen has no toxicity,     which improves the safety of production. -   3. For the calcine prepared by the device in the present     application, the purity of the target valence state vanadium in the     calcine is relatively high.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an overall structure for embodying a device for accurately controlling a reduction valence state of high-purity vanadium pentoxide in Embodiment 1 of the present application.

FIG. 2 is a schematic cross-sectional view of the overall structure for embodying the device for accurately controlling the reduction valence state of high-purity vanadium pentoxide in Embodiment 1 of the present application.

FIG. 3 is a schematic structural view for embodying a weighing member in Embodiment 1 of the present application.

FIG. 4 is a table of performance detection results in accordance with examples described herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present application will be further described below in detail with reference to examples.

All raw materials in the examples are commercially available.

EXAMPLES Example 1

A device for accurately controlling a reduction valence state of high-purity vanadium pentoxide is disclosed in Example 1.

With reference to FIG. 1 , a device for accurately controlling a reduction valence state of high-purity vanadium pentoxide comprises a conveying member and a casing 2 arranged on the conveying member. A partition member is provided on the casing 2, and a material storage member and a weighing member 5 are also provided on the conveying member.

With reference to FIGS. 1 and 2 , the conveying member comprises a chain conveyor 1, the casing 2 is fixedly connected on a frame 12 of the chain conveyor 1, and two opposite side walls of the casing 2 are each provided with a through hole 29 through which the material storage member passes; the partition member comprises a partition plate 3 fixedly connected on the inner top wall of the casing 2, the partition plate 3 is vertically arranged, the partition plate 3 divides the inside of the casing 2 into a reduction zone 21 and a protection cooling zone 22, and a space through which the material storage member passes is reserved below the partition plate 3; the material storage member comprises a material tray 4 placed on the chain conveyor 1, the material tray 4 is located between two adjacent power rollers 11 on the chain conveyor 1, and the length of the material tray 4 is greater than the width of the chain conveyor 1; two ends of the material tray 4 extend out from the chain conveyor 1 along the width direction of the chain conveyor 1, the material of the material tray 4 may be zirconia or alumina, and the material of the material tray 4 in this embodiment is alumina; the chain conveyor 1, the inner wall of the casing 2, and the partition plate 3 are all coated with high-temperature resistant paint; and silicon carbon rods 6 are installed on the inner top wall of the casing 2, and the silicon carbon rods 6 are located in the reduction zone 21.

With reference to FIG. 3 , the number of weighing members 5 is two, and two weighing members 5 are both arranged on the frame 12 of chain conveyor 1, wherein one of the weighing members 5 is positioned at a feeding end of the chain conveyor 1 end, and the other of the weighing members 5 is located below the reducing zone 21 in the casing 2; the weighing member 5 comprises a mounting plate 51 fixedly connected on the frame 12 of the chain conveyor 1, and the mounting plate 51 is arranged horizontally; a load cell 52 is installed on the top wall of the mounting plate 51, the weighing end of the load cell 52 is fixedly connected with a connecting plate 53, and the connecting plate 53 is horizontally arranged; a sliding hole 121 through which the connecting plate 53 passes is provided on the frame 12 of chain conveyor 1, and two ends of the connecting plate 53 are slidingly connected on the wall of the sliding hole 121; two electric cylinders 54 are installed on the top wall of the connecting plate 53, and the two electric cylinders 54 are located at two ends of the connecting plate 53, respectively; and telescopic rods of the two electric cylinders 54 are each fixedly connected with a vertical plate 55, and the two vertical plates 55 are both vertically arranged; two weighing holes 23 are provided on the bottom wall of the casing 2, and the two vertical plates 55 located below the reduction zone 21 are both coated with high-temperature resistant paint, wherein one of the vertical plates 55 is slidably connected on the hole wall of one of the weighing holes 23, and the other of the vertical plates 55 is slidably connected on the wall of the other of the weighing holes 23.

With reference to FIG. 1 , a gas cylinder 7 is installed on the outer top wall of the casing 2, a scraper 71 is fixedly connected on a piston rod of the gas cylinder 7, the scraper 71 is vertically arranged, and the piston rod of the cylinder 7 drives the scraper 71 to move downward. During the process of the chain conveyor 1 conveying vanadium pentoxide, the scraper 71 scrapes vanadium pentoxide in the material tray 4, so that vanadium pentoxide is evenly distributed on the material tray 4.

With reference to FIG. 1 , a first gas inlet 25 and a first gas outlet 26 are provided on the top wall of the casing 2, the first gas inlet 25 and the first gas outlet 26 are both in communication with reduction zone 21, and a pressure gauge 8 is installed at each position close to the first gas inlet 25 and the first gas outlet 26 on the top wall of the casing 2; and a second gas inlet 27 and a second gas outlet 28 are provided on the top wall of the casing 2, both the second gas inlet 27 and the second gas outlet 28 are in communication with the protection cooling zone 22, and a pressure gauge 8 is installed at each position close to the second gas inlet 27 and the second gas outlet 28 on the top wall of the casing 2.

A method for accurately controlling a reduction valence state of high-purity vanadium pentoxide is also disclosed in Example 1.

A method for accurately controlling a reduced valence state of high-purity vanadium pentoxide comprises the following steps: Reduction: two electric cylinders 54 located at a feeding end of a chain conveyor 1 drive vertical plates 55 to rise, and the vertical plates 55 lift a material tray 4; vanadium pentoxide is added to the material tray 4, and a load cell 52 weighs until 10 g of vanadium pentoxide is added; then, the electric cylinders 54 drive the vertical plates 55 to move downward, the material tray 4 falls to the chain conveyor 1, and the chain conveyor 1 conveys vanadium pentoxide to a reduction zone 21; during the conveyance process, a piston rod of a gas cylinder 7 drives a scraper 71 to move downward, and the scraper 71 scrapes vanadium pentoxide in the material tray 4; a first gas inlet 25 is used to introduce hydrogen into the reduction zone 21 at a rate of 280 ml/min, and at the same time, the reducing gas is discharged through a first gas outlet 26; and a silicon carbon rod 6 is used to heat, so that the temperature in the reduction zone 21 is 630° C., and vanadium pentoxide undergoes a reduction reaction to obtain the mixture;

Weighing: when the material tray 4 is above the two vertical plates 55 and below the reduction zone 21, the chain conveyor 1 stops conveying, two electric cylinders 54 below the reduction zone 21 drive the vertical plates 55 to rise, the vertical plates 55 lift the material tray 4, and the mixture in the material tray 4 is weighed; a target valence state is set to 3.5-valence, and it is calculated according to the mass of the added vanadium pentoxide that the weight of the completely generated 3.5-valence vanadium product should be 8.76 g; and when the weight of the mixture is 8.76 g, the electric cylinders 54 drive the vertical plates 55 to move downward, the chain conveyor 1 takes the mixture out of the reduction zone 21, the reaction is stopped, and the reaction time is 105 min at this time;

Cooling: a second gas inlet 27 is used to introduce nitrogen into a protective cooling zone 22, and at the same time, a second gas outlet 28 is used to discharge nitrogen to cool the mixture, so as to obtain calcine; and a pressure gauge 8 is used to observe the reduction zone 21 and the protective cooling zone, to ensure that the gas pressure in the protection cooling zone 22 is greater than the gas pressure in the reducing zone 21.

Example 2

The difference between Example 2 and Example 1 is that the rate at which hydrogen is introduced is 220 ml/min, and the temperature in the reduction zone 21 is 680° C.; the target valence state is set to be 3.0-valence, and it is calculated according to the mass of the added vanadium pentoxide that the weight of the completely generated 3.0-valence vanadium product should be 8.32 g; and when the weight of the mixture is 8.32 g, the chain conveyor 1 takes the mixture out of the reduction zone 21, the reaction is stopped, and the reaction time is 228 min at this time.

Example 3

The difference between Example 3 and Example 1 is that the rate at which hydrogen is introduced is 200 ml/min, and the temperature in the reduction zone 21 is 650° C.; the target valence state is set to be 4.0-valence, and it is calculated according to the mass of the added vanadium pentoxide that the weight of the completely generated 4.0-valence vanadium product should be 9.21 g; and when the weight of the mixture is 9.21 g, the chain conveyor 1 takes the mixture out of the reduction zone 21, the reaction is stopped, and the reaction time is 62 min at this time.

Example 4

The difference between Example 4 and Example 3 is that when nitrogen is introduced into the protection cooling zone 22, the gas pressure in the protection cooling zone 22 is less than the gas pressure in the reduction zone 21.

COMPARATIVE EXAMPLES Comparative Example 1

3.5-valence vanadium is prepared with reference to Example 1 in the Chinese patent whose announcement number is CN110867602A.

Comparative Example 2

The difference between Comparative Example 2 and Example 2 is that the mixture is directly taken out after the reduction reaction, and cooled at room temperature to obtain calcine.

The purity of target valence state vanadium in a performance detection test is: average valence state of vanadium=(vanadium content/51)/[(1-vanadium content)/16]*2, that is, the closer the average valence state of vanadium is to the target valence state, the higher the purity of target valence state vanadium in the calcine, wherein

the vanadium content is detected using an emission spectrometer with model 725-ICP-OES.

FIG. 4 shows a performance detection result table (Table 1) in accordance with examples described herein.

With reference to Example 1 and Comparative Example 1, since the average valence state of vanadium in Example 1 is closer to the target valence state, the purity of target valence state vanadium in Example 1 is higher. As can be seen, with the method of the present application, the progress of the reaction is judged according to the change of the weight of the reduction reaction product, which reduces the generation of non-target valence state vanadium, and thus improves the purity of the target valence state vanadium in the calcine.

With reference to Example 2 and Comparative Example 2, since the average valence state of vanadium in Example 2 is closer to the target valence state, the purity of target valence state vanadium in Example 2 is higher. As can be seen, after the reduction reaction, the cooling gas is used to cool the mixture, which has a certain protective effect, avoids the contact of the mixture with air, and uses its own residual temperature to oxidize, thereby improving the purity of the target valence state vanadium in the calcine.

With reference to Examples 1 to 3, the average valence states of vanadium in Examples 1 to 3 are all close to the target valence state. Thus, as can be seen, the use of the method in the present application can accurately control the reduction valence state of vanadium pentoxide, and the purity of the target valence state vanadium in obtained calcine is relatively high.

With reference to Examples 3 and 4, since the average valence state of vanadium in Example 3 is closer to the target valence state, the purity of target valence state vanadium in Example 3 is higher. As can be seen, when the cooling gas is introduced, the gas pressure in the protection cooling zone is made greater than the gas pressure in the reduction zone, which can prevent the reducing gas in the reduction zone from entering the protection cooling zone, and thus avoids the further reduction reaction of the mixture when it is cooled in the protection cooling zone, thereby improving the purity of the target valence state vanadium in the calcine.

These specific examples are only an explanation of the present application, and are not intended to limit the present application. A person skilled in the art can make modifications without creative contribution to these examples after reading the present specification, as long as they are protected by the patent law within the scope of the claims of the present application. 

What is claimed is:
 1. A method for controlling a reduction valence state of high-purity vanadium pentoxide, the method comprising: introducing a reducing gas into the vanadium pentoxide to carry out a reduction reaction under a heating condition to obtain a mixture; weighing the mixture during the reduction reaction, and stopping the reaction when the weight of the mixture reaches a specified value; and introducing a cooling gas into the mixture for cooling the mixture to obtain calcine.
 2. The method according to claim 1, wherein the reducing gas comprises one of hydrogen, carbon monoxide or sulfur dioxide.
 3. The method for accurately controlling the reduction valence state of the high-purity vanadium pentoxide according to claim 1, wherein a rate at which the reducing gas is introduced is 1 to 500 ml/min.
 4. The method according to claim 1, wherein the introducing the reducing gas comprises heating using a silicon carbon rod at a temperature from 300° C. to 1200° C.
 5. The method according to claim 1, wherein the cooling gas comprises nitrogen or an inert gas.
 6. A device comprising: a conveyor and a casing on the conveyor; a partition, provided on the casing, configured to divide an inside of the casing into a reduction zone and a protection cooling zone; a material storage configured to store materials on the conveyor; and a weighing member provided on the conveying member.
 7. The device according to claim 6, wherein the conveying member comprises a chain conveyor, wherein the casing is on a frame of the chain conveyor, wherein the partition member comprises a partition plate, arranged on an inner top wall of the casing, and configured to divide the inside of the casing into the reduction zone and the protection cooling zone, wherein the material storage member comprises a material tray on the chain conveyor and between two adjacent power rollers on the chain conveyor, and wherein both ends of the material tray extend out along a width direction of the chain conveyor.
 8. The device according to claim 7, wherein the weighing member comprises a load cell on the frame of the chain conveyor, wherein a weighing end of the load cell is connected with a connecting plate, wherein the connecting plate is connected with two electric cylinders, wherein telescopic rods of the two electric cylinders are each connected with a vertical plate, and wherein the two vertical plates are used to lift the material tray.
 9. The device according to claim 7, wherein the material tray comprises zirconia or alumina.
 10. The device according to claim 6, wherein a gas pressure in the protection cooling zone is greater than a gas pressure in the reduction zone. 